1) an old grey cat, especially female; 2) an untidy woman...



A desert place. Thunder and lightning. -
Enter three Witches. -

FIRST WITCH. When shall we three meet again? In thunder, lightning, or in rain?


FIRST WITCH. I come, Graymalkin.

SECOND WITCH. When the hurlyburly's done, When the battle's lost and won.


ALL. Paddock calls. Anon!

Fair is foul, and foul is fair.

Hover through the fog and filthy air. Exeunt.

  THIRD WITCH. That will be ere the set of sun.  
FIRST WITCH. Where the place?
  SECOND WITCH. Upon the heath.      
  THIRD WITCH. There to meet with Macbeth.  

In the opening scene of Macbeth, one of the three witches planning to meet with Macbeth suddenly announces, "I come, Graymalkin." The witch is responding to the summons of her familiar, or guardian spirit, which is embodied in the form of a cat. Shakespeare's "graymalkin" literally means "gray cat." The "gray" is of course the color; the "malkin" was a nickname for Matilda or Maud that came to be used in dialect as a general name for a cat (and sometimes a hare), and for an untidy woman as well. By the 1630s, "graymalkin" had been altered to the modern spelling "grimalkin."
(Merriam-Webster Online Word of the Day, March 5, 2004)